Hydraulic elevator control systems



Aug. 16,

Filed Sept.

R. F. LOUGHRIDGE HYDRAULlC ELEVATOR CONTROL SYSTEMS 5 Sheets-Sheet l 27 RESERVOIR 57 PUMP sv-4 N-4 I /5 L UP CONTROL FLOOR Q55 BY-PASS N-l N-Z A w VALVE N-3 sv-s 29 SV-l ,fl5

DOWN PILOT J /9 VALVE wmg JACK -"/07 an 25 17 2/ CHECK 15 VALVE INYENTOR. fiaew/ fwykwa /qe Aug; 16, 1966 R. F. LOUGHRIDGE 3,266,382

HYDRAULIC ELEVATOR CONTROL SYSTEMS Filed Sept. 24, 1964 5 Sheets-Sheet 2 INVENTOR.

Aug. 16, 1966 R. F. LOUGHRIDGE HYDRAULIC ELEVATOR CONTROL SYSTEMS Filed Sept. 24, 1964 OPEN OPEN

5 Sheets-Sheet 5 sv-a J CLOSED- OPEN CLOSED PUMP MOTOR J OFF L i-I FLOOR A OPEN- CLOSED L OPEN FLOOR B) SV-I J CLOSED...

ON PUMP MOTOR OFF- I; 1-4 FLOOR B CAR CONTROLLER FLOOR A PUMP MOTOR SV-l CONTROLLER (NC) SV-5 (N.O.)

J75 CAM SELECTO R CONTROLLER IN VEN TOR.

United States Patent 3,266,382 HYDRAULIC ELEVATOR CONTROL SYSTEMS Robert F. Loughridge, 2343 Winton Terrace W-, Fort Worth, Tex. Filed Sept. 24, 1964, Ser. No. 398,924 8 Claims. (Cl. 91-468) My invention relates in general to hydraulic control systems for elevators, and more particularly to hydraulic elevator control systems which are used to control the speed of the elevator while moving in the upward direction.

One of the most successful systems for con-trolling the speed of elevator cars travelling in an upward direction, particularly during levelling, utilizes one or more by-pass valves to divert the flow of fluid from the hy draulic jack or ram that propels the elevator car. The speed of the elevator is, of course, a function of the quantity or flow rate of the fluid which passes to the hydraulic jack. Thus the by-pass valve is used to control the rate of fluid flow to the hydraulic jack. However, such systems controlled in accordance with the teachings of the prior art of which I am aware, are subject to some disadvantages. For one thing, it is difficult to achieve a constant elevator speed during uplevelling. This problem is often the result of variations in system pressure due to variations in elevator load. That is, changes in elevator load alter the fluid pressure in the hydraulic jack and this pressure variation is not effectively reflected by the control system.

The general object of my invention is to provide an improved up-control system for hydraulic elevators.

Another object of my invention is to provide a hydraulic elevator uplevelling control system that is capable of dealing effectively with pressure variations in the elevator jack.

Another object of my invention is to provide an improved hydraulic elevator control system that is capable of producing constant up-level-ling speeds independant of variations in elevator loads.

Another object of my invention is to provide a simplified up-levelling control system by decreasing the compleXity of the principal components of the system. The accomplishment of this object will, of course, lead to increased economy by decreasing initial costs and maintenance problems.

These and other objects of my invention will become apparent from the following description, taken in accordance with the accompanying drawings, in which:

, FIG. 1 is a schematic longitudinal sectional view of an lip-control by-pass valve constructed in accordance with a preferred embodiment of my invention.

FIG. 2 is a schematic longitudinal section of a downcontrol valve.

FIG. 3 is a schematic diagram of the fluid system of a hydraulic elevator in accordance with a preferred embodiment of my invention.

FIG. 4 is a sectional view taken along the line IVIV of FIG. 1.

FIG. 5 is a fragmentary side elevational view of a flow responsive or check valve with a pilot valve assembly therewith.

FIG. 6 is a sectional view which shows in better detail the structural features of the pilot valve shown to some extent in FIG. 5.

FIGS. 7 and 8 are sectional views taken respectively along the lines VIIVII and VIIIVIII of FIG. 6.

FIGS. 9 and 10 are graphs that aid in the explanation of the operation of the hydraulic fluid system shown in FIG. 3.

FIG. 11 is a schematic diagram of electrical controls which pertain to the system of FIG. 3.

Patented August 16, 1966 Referring now to the drawings and initially to FIG. 3 for an over-all description of the apparatus, the numeral 111 designates a fluid reservoir which is preferably located in an elevated position with respect to a fluid pump 13, normally operated by an electric motor (not shown). A primary conduit 15 connects a pump 13 with a hydraulic jack 17. A bypass conduit 19 communicates with primary conduit -15 and the junction 21, it will be noticed, is located upstream (i.e., toward the pump) from a check valve 23. The by-pass conduit 19 commun-icates with an lip-control lay-pass valve 25 and ultimately with a return line 2-7 that is connected with fluid reservoir 11.

A pilot valve 29 is interposed in a pilot conduit 31 that connects the check valve 23 with the up-control bypass valve 25 by way of a solenoid valve SV-S.

A dump line 33 communicates with primary conduit 15 upstream from the point of communication 21 between lay-pass conduit v19 and primary conduit 15, said dump line communicating with the return line 27 through needle valve N-3, solenoid valve SV-3, and solenoid valve SV-4. The dump line 3-3 and the up-control bypass valve 25 are connected 'by a conduit 35, which in turn is connected by a conduit 37 to the by-pass conduit 19. The conduit 37 contains a needle valve N-4.

That part of the system thus far described constitutes the up-control system of the over-all elevator control system. The down-control system will be described in detail later to provide a basis for a more complete understanding of my invention but it should be understood that my present invention is directed to the up-control system.

The purpose of the up-control system is to control the movements of the car 39 While moving in the upward direction. The car speed is controlled by the flow rate of the fluid which reaches the hydraulic jack 17 by means of primary conduit 15. The speed of the car may be reduced by diverting the fluid from the primary conduit 15 through the by-pass conduit 19 by opening the upcontrol valve 25. A critical time for accurate speed control is during the uplevelling period of the cycle. The uplevelling period of the cycle is that period during which the elevator approaches a floor (such as floor A in FIG. 3) at a pre-selected reduced rate of speed. The system of controlling the uplevelling speed, in accordance with the embodiment shown, utilizes the check valve 23, which may be broadly'described as a flow responsive device, in conjunction with the pilot valve 29 which actuates and thus controls the setting of the up-control valve 25. Be fore a comprehensive operational description of my system is given, the structural detailed description of the check valve or flow responsive device 23, the pilot valve 29, and the up-control by-pass valve 25 will be given.

Referring now to FIG. 5 of the drawing it will be seen that the check valve 23 includes the body 41 which is interposed in and connected with the primary conduit 15. Fluid flows through the flow responsive device or valve 23 in the direction as indicated by the letter A. Inside the interior of the body 41 is a flow responsive member or movable element 43, the position of which is directly controlled by the flow rate of the fluid passing through the valve 23. Movable element 43 has a stem 45 which is slidably mounted on support arm 45. A coil spring 49 surrounds the stem 45 and engages supportarm 47 and movable element 43 to urge the movable element downward into engagement with the annular lip 51. In the preferred embodiment the flow responsive valve 23 is in reality a check valve since the fluid can flow only in the direction indicated by the arrow A. As will be more apparent in view of the following discussion, my invention is not limited to use with checkvalves per se but may be 3 used with flow responsive devices in general which have movable elements that respond to changes in flow rate.

The pilot conduit 31 communicates between the flow responsive valve 23 and the up-control by-pass valve 25 as was previously explained. The pilot valve 29 is interposed in pilot conduit 31 and has a control arm 53 which is actuated by the movable element 43 of the flow responsive valve. Arm 53 has a stepped flange which is urged against a valve core 57 by means of a coil spring 59, one end of which engages a lip 61 on a valve body 63 as is apparent in the sectional view illustrated in FIG. 6.

Stepped flange 55 has a plurality of apertures 65, as is apparent in FIG. 8. With the control arm 53 in a horizontal position as shown in FIG. 6, the stepped flange 55 sealingly engages the end of valve core 57, preventing fluid from passing through the aperture 67 in the valve body. An O-ring 69 or other suitable sealing means is provided to prevent fluid from leaking past the space between valve core 57 and valve body 63. Thus, when the flow rate of the fluid passing through the check valve or flow responsive device 23 is large, the movable element or flow responsive member 43 will be moved away from the control arm 53. Consequently, no fluid will pass through pilot valve 29 due to the sealing engagement of the stepped flange 55 of the control arm and the end of the valve core 57. As the rate of fluid flow through flow responsive valve 23 decreases, however, the movable element 43 moves downward and ultimately into engagement with the control arm 53. This engagement tilts control arm 53 as shown in FIG. and permits fluid to flow through the pilot valve 29 and to the up-control bypass valve 25.

To prevent suction and to enable the stepped flange 55 to easily move away from the end of the valve core 57, an annular groove 71 is provided in the end of the core 57. At the opposite end of the valve core 57 is a grasping means 73 which can be used to engage or disengage the valve core 57 and the valve body 63, such members being in this embodiment mutually engageable by means of the threads 75. The valve body 63 is threaded at 77 on the exterior thereof so that it may be attached to the flow responsive valve 23. To effect a better seal therewith, an O-ring 79 is provided in the groove 81 which surrounds the forward end of the body. The valve body has a head 83 which may be grasped and rotated to extend or retract the pilot valve into or from the body 41 of the flow responsive valve 23. This also enables adjustment of the levelling speed of the elevator since the end of the control arm 53 is contoured to have a conical surface as designated by the numeral 85 so that axial extension or retraction determines the extent of the deflection of the arm by the cooperation of movable element 43 for any given flow rate passing through the primary conduit 15 and the flow responsive valve 23.

As was explained previously, the fluid flows through pilot valve 29 and solenoid valve SV-5 during up-leveling of the elevator car to control the flow of fluid to, and thus the setting of, the up-control bypass valve 23. Referring now to FIG. 1 of the drawings for a detailed description of the structure of a preferred embodiment of the upcontrol by-pass valve 25, it will be seen that the pilot conduit 31 communicates with a passage 87 that extends through a lower plug 89 attached to the valve body 91. A cylindrical cavity 93 is formed on the interior of the body 91 and slidably engages a piston 95, which is the lower portion of a floating valve element 97. This floating valve element is adapted to engage a valve seat 99 which is formed on the interior of the valve body 91. Thus, the amount of fluid flowing through pilot conduit 31 and passage 87 of the lower plug 89 controls the setting of the floating valve element 97 and thus the amount of fluid which flows through the by-pass conduit 19 as shown in general by the arrow B in FIG. 1. The valve body 91 has an inlet aperture 101 and an outlet aperture 103 so that it may be easily inserted in the by-pass conoutlet aperture 113. These apertures are, of course, connected to the down-control conduit which communicates with the primary conduit 15 and the return line 27 as shown in FIG. 3. Internally, the valve 107 is fitted with a valve seat 117 supported by structure 119 integrally attached to the valve body 199, and a valve aperture 121 through which fluids may flow. The valve body 109 has a main valve cavity 123, a mid-body cavity 125 and an upper body cavity 127 and a threadedly connected valve body cap 129. An O-ring gasket 131 effectively seals the joint between the valve body 1119 and the body cap 129.

Within the mid-body cavity 125 there is a valve disc 133. This disc is integrally connected by a cylinder 135 to a piston 137, preferably of circular shape and larger in diameter than the valve disc 133. The piston 137 is sildeable in the upper body cavity 127 and has a groove 139 in its periphery which is adapted to receive a sealing device 141 to prevent the flow of fluids thereby.

Centered in the valve body cap 129 is an adjustable elongated spindle 143, the upper portion of which is threaded into the valve body cap 129, while the lower portion is cylindrical and is slideable in a central cavity 145 which is located both in the piston 137 and in the cylinder 135. The spindle 143 has a central longitudinal cavity 147 extending for approximately threequarters of its length from the top end, and there is an orifice 149 in the tubular wall near the bottom of the cavity 147 which affords communication with the upper body cavity 127 and the central cavity 147. A look nut 151 encircles the adjustable spindle 119 and holds it in fixed relation to the piston 137.

An adjustable stop bolt 153 and lock nut 155 are inserted through the valve body cap 129 a suflicient distance to limit the upper movement of the piston 137 when the valve opens. (FIG. 2 illustrates the valve 107 in the closed position.) The valve body cap is also fitted with a passage 157 and threaded cavity 159 which affords communication between the upper body cavity 127 and a threadedly connected conduit means (not shown).

A series of connected passages 161 afford communication between the mid-body cavity 125 and the upper body cavity 127. An adjustable needle valve 163 is provided in a convenient location to regulate the flow of fluid through the passages 161.

The lower periphery of the valve body 109 is fitted with an axially threaded boss 165 to which an adjustable rotatable stem 167 is threaded. The lower extremity of the stem 167 is provided With a rotating means, preferably a hand wheel 169, secured to the stem 167 by a nut 171.

The electrical controls illustrated with the schematic diagram of FIG. 7 include a car controller 173, a cam selector controller 175, a pump motor controller 177 and the solenoid valves SV1 through SV-5. The function of these controls will become subsequently apparent during the description of the operation of the system.

To understand the manner in which my improved hydraulic elevator up-control system operates, it will be helpful to consider the sequence of operation required to move an elevator car 39, initially at rest, from floor A to floor B, and then to lower the car from floor B to floor A.

With a car at floor A and at rest, the following conditions prevail: The system is full of hydraulic fluid and the reservoir 11 is filled to its normal operating level; the down-control valve 1117 is closed and the load on the car 39 and jack 17 is held by the check valve 23 which is closed. The pilot valve 29 is thus held in the open position since the control arm 53 is pivoted downwardly by the engagement of the closed movable element 43 of check valve 23, as is shown in FIG. 5. At this stage the pump is not in operation since no fluid is flowing in the system.

To start upward, the up button (not shown) but a part of the car controller generally indicated as a block 173 in FIG. 11, is pushed at time Tl in FIG. 5, whereupon power is applied to the motor (not shown) starting the pump 13. Electrical power is applied to the solenoid valves SV3, SV4 and SV-5. Valve SV4 closes, which prevents fluid from flowing through the dump line 33, to shunt all of the control fluid into the up-control by-pass valve 25. Solenoid valve SV-S closes, cutting off the flow of fluid from the pilot valve 29 during the initial starting of the elevator. This is beneficial in preventing fluid in the vicinity of check valve 23 from affecting the up acceleration of the elevator. Solenoid valve SV3 opens, allowing fluid to flow through the needle valve N-3 into the up-control by-pass valve 25. The resulting increased fluid pressure exerted on the lower side of the piston 95 through the passage 87 in the lower plug 89 of the up-control by-pass valve 25 (see FIG. 1) causes the valve to close. Consequently, the quantity of fluid flowing to the hydraulic jack 17 through primary conduit is maximized and the car quickly accelerates to full speed.

As the car 39 approaches floor B, a stopping sequence is initiated by cam selector controller 175 at time T3 and at this time solenoid valves SV3 and SV-5 are deenergized. Valve SV3 closes, shutting off the flow of control fluid from the needle valve N-3 to the up-control by-pass valve 25, and solenoid valve SVS opens. The fluid now bleeds from the up-control *by-pass valve 25 through the slow-down orifice or needle valve N-4. Thus the upward force exerted on the piston 95 by the control fluid is decreased and the up-control by-pass valve 25 begins to open. Since this event enables fluid to flow through the by-pass conduit 19 and to the reservoir 11 via the return line 27, the flow of fluid through the primary passage 15 and to hydraulic jack 17 is decreased and the car begins to slow down. As the speed of the car decreases, the movable element 43 in the check valve 23 begins to close. As the speed of the car continues to decrease, the movable element 43 of check valve 23 will close enough to begin opening the pilot valve 29 by tilting the control arm 53. When this happens, fluid will flow through pilot valve'29, pilot conduit 31, solenoid valve SV- S, and passage 87 in the lower plug 89 of the upcontrol =by-pass valve 25. u The flow of fluid from the pilot valve 29 to the 'by-pass valve will cause a buildup of pressure on the lower surface 96 of the piston 95 until such time as the resulting force acting on the piston lower surface 96 equals that acting on the piston upper surface 98, at which time the floating valve element 97 will cease its downward (opening) movement, thus establishing the preselected lip-levelling speed for the elevator car. This preselected up-levelling speed is maintained essentially constant by the regulating action of the control system. More particularly, if the up-levelling speed tends to increase or decrease, the flow rate of fluid passing through the check valve 23 will tend to increase or decrease, causing movement of the check valve movable element 43 and consequent opening or closing movement of the pilot valve 29 so as to produce a pressure charge on the lower surface 96 of the by-pass valve piston 95. This pressure charge will affect the position of the floating valve element 97 in a manner which will tend to maintain the flow rate of fluid passing through the check valve 23 constant, with the result that the up-levelling speed of the elevator car will be maintained essentially constant.

The car 39 will continue to travel at a constant uplevelling speed until floor B is reached, at which time the electrical circuit to the pump motor controller 177 opens and the solenoid valve SV4 opens. Opening solenoid valve SV4 dumps the control fluid from the up-control by-pass valve, which then opens to divert all fluid flow through the by-pass conduit 19, thus stopping the car.

In order to describe the operation of the down-control system when lowering the car 39 from floor B to floor A, reference is made to FIGS. 2, 3 and 6.

The following conditions prevail when the car 39 is at rest at floor B. The pump 13 is not operating; the. check valve 23 is closed and holding the car 39 and its load, if any, at floor B; the down-control valve 107 is closed and both the solenoid valves SV-l and SV2 are closed.

The purpose of down-control valve 107 may be understood more completely by observing that, while closed, the fluid in the system entering the valve in the direction of the arrow C, flows past the flat sides of the valve disc 133 (similar to the apertures 92 shown in FIG. 4) and fills the mid-body cavity below the piston 137. Fluid passing the needle valve 163 enters the passage 161 and fills the upper body cavity 127. Fluid in this cavity has two possible routes of flow; via the outlet 157 which cornmunicates via line 108 with the solenoid valve SVI, or via the orifice 149 which communicates via the central cavity and the line 110 with the solenoid valve SV2. Since the area of the upper side of the piston 137 is greater than the area of the underside thereof, the downcontrol valve 107 remains in a closed position.

To start downward, the down button (on car controller 173) is pushed at time T-4 (see FIG. 10), whereupon the solenoid valve SV-1 opens while solenoid valve SV2 remains closed. Fluid in the upper body cavity 127 flows via line 108 through the solenoid valve SV1 to the return line 27 and thus to the fluid reservoir 11. Since. the pressure differential holding the down-control valve 107 closed no longer exists, the down-control valve begins to open. Fluid can flow from the hydraulic jack 17 through the partially open down-control valve 107, and this causes the elevator car 39 to begin to move downward. As fluid flows through the down-control valve 107 and via line 177 back to the reservoir 11, the down-control valve 107 continues to open until piston 137 strikes the adjustable stop bolt 153. ,In this position the piston 137 covers orifice 149 and no fluid flows through it.

As the elevator car approaches floor A, at time TS, a cam on the cam selector controller actuates a switch which closes an electric circuit energizing the solenoid valve SV-2, which then opens.

While car 39 continues to descend and approach floor A, at time T-6, another cam on the cam selector controller 175 actuates a switch which de-energizes solenoid valve SV-l, which closes. Fluid, nevertheless, continues to flow into the upper body cavity 127 and, since there is no open passage by which it can escape, the fluid pressure builds up on the upper surface of the piston 137. Imrnediately, the pressure builds up and the piston moves downward toward the closed position; however, when the orifice 149 is uncovered again, fluid flows through it at a rate equal to the flow past the needle valve 163 and through the passages 161 into the cavity. Fluid now flows via the line 110 and the solenoid valve SV-2 into the down-control conduit 115, through return line 27 and to the fluid reservoir 11. At this moment, the downward movement of the piston 137 ceases; the down-control valve 107 is partially closed, and the car descends from floor B at a uniform levelling speed, which is some proportionate part of the open valve speed.

At the moment the car reaches the level of floor A, at time T7 of FIG. 10, another cam on the cam selector controller 175 actuates a switch which opens a circuit causing the solenoid valve SV-2 to close. The closing of the valve SV2 produces immediately a buildup of diflerential pressure downward on the piston 137, and the down-control valve 107 closes. In this situation all the fluid in the hydraulic jack 17 is held 'by the check valve 23 and the car 39 remains at floor A.

It should be apparent from the foregoing that I have provided a hydraulic elevator up-control system having significant advantages.

My invention derives from the realization that if the' flow rate of fluid passing into the elevator jack is maintained constant, then the speed .of the elevator car will be maintained constant. In accordance with the principles of my invention, the rate of fluid flow to the jack is sensed directly and within a region wherein the flow rate sensed is in effect the flow nate of fluid into the jack. This manner of flow rate sensing obviates complications, complexities and "other disadvantages which have accompanied prior art techniques.

It should be understood that the foregoing disclosure and the showings made in the drawings are merely illustrative of the principles of my invention and are not to be interpreted in a limited sense. The flow rate sensing device (flow responsive valve or device) may be disposed anywhere within the region of the primary conduit that is intermediate the hydraulic jack and the junction of the primary and by-pass conduits. The flow rate sensing device nray be any device that is capable of directly sensing the flow rate. If the flow rate sensing device is a check valve, then of course it must be disposed upstream (on the pump side) of the junction of the primary and down-control conduits.

I claim:

1. In a hydraulic elevator up-control system of the type having a primary conduit that connects a pump to a hydraulic jack, and a by-pass conduit which communicates with said primary conduit and which includes bypass valve means for diverting a portion of the flow of fluid from said pump away from said hydraulic jack as a means of controlling the speed of the elevator, the improvement comprising:

(a) a flow responsive valve interposed in said primary conduit at a region intermediate the hydraulic jack and the junction of the primary and bypass conduits, said flow responsive valve having a movable element the position of which is directly controlled by the flow rate of the fluid passing through said valve;

(b) a pilot conduit communicating between said flow responsive valve and said by-pass valve means; and

(c) a pilot valve attached to said flow responsive valve and having a control arm that is biased to urge said pilot valve toward its closed position, said arm extending into engagement with the movable element of said flow responsive valve to actuate the pilot valve to control said by-pass valve means.

2. The invention as defined by claim 1, wherein said flow responsive valve is a check valve.

3. In a hydraulic elevator up-control system of the type having a primary conduit that connects a pump to a hydraulic jack, and a by-pass conduit which communicates with said primary conduit and which includes bypass valve means for diverting a portion of the flow of fluid from said pump away from said hydraulic jack as a means of controlling the speed of the elevator, the improvement comprising:

(a) a flow responsive valve interposed in said primary conduit at a region intermediate the hydraulic jack and the junction of the primary and by-pass conduits,

said flow responsive valve having a movable ele- 60 ment the position of which is directly controlled by the flow rate of the fluid passing through said valve;

'(b) a pilot conduit communicating between said flow responsive valve and said by-pass valve means; and

(c) a pilot valve interposed in the pilot conduit and having a control arm that engages the movable element of said flow responsive valve to actuate the pilot valve to control said bypass valve means.

4. The invention as defined by claim 3, wherein said flow responsive valve is a check valve.

5. In a hydraulic elevator up-control system of the type having a primary conduit that connects a pump to a hydraulic jack, and a by-pass conduit which communicates with said primary conduit and which includes by-pass valve means for diverting a portion of the flow of fluid from said pump away from said hydraulic jack as a means of controlling the speed of the elevator, the improvement comprising:

(a) a flow responsive valve interposed in said primary conduit at a region intermediate the hydraulic jack and the junction of the primary and by-pass conduits, said flow responsive valve having a movable element the position of which is directly controlled by the flow rate of the fluid passing through said valve;

(b) a pilot conduit communicating between said flow responsive valve and said by-pass valve means; and

(c) a pilot valve interposed in the pilot conduit and actuated by the movable element of said flow responsive valve to control said by-pass valve means.

6. The invention as defined by claim 5, wherein said flow responsive valve is a check valve.

'7. In a hydraulic elevator up-control system of the type having a primary conduit that connects a pump to a hydraulic jack, and a by-pass conduit which communicates with said primary conduit and which includes bypass valve means for diverting a portion of the flow of fluid from said pump away from said hydraulic jack as a means of controlling the speed of the elevator, the improvement comprising:

(a) a flow responsive device interposed in said primary conduit at a region intermediate the hydraulic jack and the junction of the primary and by-pass conduits, said flow responsive device having a movable element the position of which is directly controlled by the flow rate of the fluid passing through said device;

(b) a pilot conduit communicating between said flow responsive device and said by-pass valve means; and

(c) a pilot valve interposed in the pilot conduit and actuated by the movable element of said flow responsive device to control said by-pass valve means.

8. The invention as defined by claim 7, wherein said flow responsive device is a check valve.

References Cited by the Examiner UNITED STATES PATENTS 2,944,401 7/1960 Beck -52 2,984,982 5/1961 Joseph 91468 X 3,141,386 7/1964 Loughridge 91-47 X EDGAR W. GEOGHEGAN, Primary Examiner.

P. T. COBRIN, Assistant Examiner. 

1. IN A HYDRAULIC ELEVATOR UP-CONTROL SYSTEM OF THE TYPE HAVING A PRIMARY CONDUIT THAT CONNECTS A PUMP TO A HYDRAULIC JACK, AND A BY-PASS CONDUIT WHICH COMMUNICATES WITH SAID PRIMARY CONDUIT AND WHICH INCLUDES BYPASS VALVE MEANS FOR DIVERTING A PORTION OF THE FLOW OF FLUID FROM SAID PUMP AWAY FROM SAID HYDRAULIC JACK AS A MEANS OF CONTROLLING THE SPEED OF THE ELEVATOR, THE IMPROVEMENT COMPRISING: (A) A FLOW RESPONSIVE VALVE INTERPOSED IN SAID PRIMARY CONDUIT AT A REGION INTERMEDIATE THE HYDRAULIC JACK AND THE JUNCTION OF THE PRIMARY AND BYPASS CONDUITS SAID FLOW RESPONSIVE VALVE HAVING A MOVABLE ELEMENT THE POSITION OF WHICH IS DIRECTLY CONTROLLED BY THE FLOW RATE OF THE FLUID PASSING THROUGH SAID VALVE; (B) A PILOT CONDUIT COMMUNICATING BETWEEN SAID FLOW RESPONSIVE VALVE AND SAID BY-PASS VALVE MEANS; AND (C) A PILOT VALVE ATTACHED TO SAID FLOW RESPONSIVE VALVE AND HAVING A CONTROL ARM THAT IS BIASED TO URGE SAID PILOT VALVE TOWARD ITS CLOSED POSITION, SAID ARM EXTENDING INTO ENGAGEMENT WITH THE MOVABLE ELEMENT OF SAID FLOW RESPONSIVE VALVE TO ACTUATE THE PILOT VALVE TO CONTROL SAID BY-PASS VALVE MEANS. 